In process automation technology, field devices are often applied, which serve for registering a process variable. Examples of such field devices are fill level measuring devices, flow measuring devices, pressure, or temperature, measuring devices, etc., which register the corresponding process variables, fill level, flow, pressure or temperature.
A large number of such field devices are manufactured and sold by the firm, Endress+Hauser.
Field devices are composed, as a rule, of a measurement transmitter and a sensor. The sensor essentially transduces the process variable into an analog, electrical signal. The actual measured value is produced in the measurement transmitter. Most often, there is in the measurement transmitter also a further processing of the raw, measured value delivered by the sensor. Thus, non-linear behavior of the sensor can be compensated in the measurement transmitter e.g. via a linearizing function.
The measured values are, as a rule, forwarded via the measurement transmitter to controllers (PLC-units), which control or monitor a process.
The forwarding of the measured values occurs in the case of modern field devices no longer in an analog manner via a 4-20 mA current loop, but, instead, digitally via a fieldbus.
Modern field devices, therefore, have a fieldbus interface, via which a bidirectional, digital communication is enabled via the fieldbus. Such field devices are very complex and must be configured and parametered at start-up and also during operation.
Known for this are corresponding operating tools (e.g. the FieldCare product of the firm, Endress+Hauser), which work with devices of multiple manufacturers.
In order to make known to the operating tools the functionality of the different field devices, standardized device descriptions are necessary, which, normally, are provided by the field device manufacturers.
Examples of such device descriptions are HART-, Profibus-, Foundation Fieldbus—device descriptions. Also known are DTMs (Device Type Managers) in the form of executable device descriptions according to the FDT standard.
For each field device, therefore, a corresponding device description must be created, before it can be integrated into an operating tool.
Already in the case of typical field devices with only a single sensor, the creation of the device descriptions is very complicated due to the large number of adjustable parameters (sometimes over 500) and their interdependencies.
Especially in analytical technology, frequently field devices are applied, which are composed of a measurement transmitter having a plurality of connected sensors. One speaks in the case of these field devices also in terms of multi-channel field devices. Associated with each measurement channel, in such case, is a certain sensor.
Typical sensors applied in analytical technology are pH-, conductivity-, and oxygen sensors.
In the case of a field device with four measurement channels, it is evident that there are 20 different possible sensor combinations. Each sensor combination is to be viewed as an individual field device, for which, therefore, its own device description must be created.
As a rule, device descriptions are produced by the device manufacturer and must be maintained by the manufacturer. The more device descriptions a device manufacturer offers, the greater is the development and maintenance effort.
For the user, the servicing of such a multi-channel, field device, i.e. a field device having at least two measurement channels, is complicated, since the user requires the suitable device description for the particular sensor combination.
On the whole, the servicing of field devices of process automation technology having at least two measurement channels is very complicated.